Multichannel multiplexer with frequency discrimination characteristics

Claim 1

A multichannel multiplexing filter structure having the properties of channelized filtering and channelized linear frequency discrimination, for use in a microwave receiving system possessing a high probability of intercept for incoming signals, comprising: a plurality of individual, relatively narrow channels; each of said channels having an individual bandpass filter; a manifold transmission line comprising two manifolds, each manifold terminating in a matched load, and a power divider and by isolators isolating said manifolds; each of said channels being set by its bandpass filter coupled to said manifold transmission line such that the even and odd-numbered channels appear on separate manifolds, through a transformer within said bandpass filter allowing a percentage of its power to be coupled into its filter if a received signal frequency is in its passband; the remaining power being absorbed in said matched loads terminating said manifolds; each of said filters having four resonators of finite unloaded Q, the unloaded Q's of all resonators being the same; each resonator having two parameters, resonant reactance and resonant frequency, the latter being fixed at the center frequency of each channel; each of said bandpass filters having the values of its circuit parameters optimized to yield a bandpass response shape such that the ratios of the output levels of all pairs of adjacent channel filters are linear with respect to a straight-line law for dB vs. frequency in the frequency range between the center frequencies of said pairs of adjacent channels, each channel working with its higher and lower-frequency neighbors to produce this same result; and means to tune each filter to match the universal response with linear frequency scale of appropriate bandwidth within less than 0.05 dB over the required range `64 MHz` for an accurate discriminator law.

Claim 10

A method for optimizing the parameters of a multiplexing filter having a plurality of individual channel bandpass filters appearing equally on two separate manifolds isolated by a power divider, with the properties of channelized filtering and channelized linear frequency discrimination, comprising the steps of: a. providing a lumped equivalent circuit representation of two adjacent channel filters, one on each manifold, selected from said plurality for analysis with respect to linearity of frequency discrimination; b. providing a set of initial parameter values for the circuit element of said equivalent circuit representation and sample frequencies at which peak error values are likely to occur for the frequency range between the center frequencies of said two adjacent bandpass filters; c. calculating, for all pairs of adjacent channel filters, the differential amplitude between the signal output of the first of any of said two adjacent filters and that of the second at the frequencies of the predicted error extreme; d. computing an error result representing the difference between said differential amplitude and a straight-line law vs. frequency; e. computing the derivatives of said errors with respect to all optimizable parameters and with respect to frequency; f. changing said initial parameter values to values predicted by said computed derivative values; g. repeating steps c, d, e and f until errors at said sample peaks are reduced and said sample peaks coincide with actual peaks in said error, such that the error in the frequency discriminator curve relative to a straight line law is a minimum equal-ripple value over the desired frequency range; h. applying the results of said previous steps to all adjacent filter channels in said multiplexing filter, thereby optimizing the values of the circuit parameters for each of said bandpass filters to yield a bandpass response shape such that the ratios of the output levels of all pairs of adjacent channel filters is linear with respect to a straight-line law for dB vs. frequency range between the center frequencies of said pairs of adjacent channel, each channel working with its higher and lower-frequency neighbors to produce this same result; and i. tuning each filter to match the universal response with linear frequency scale of appropriate bandwidth within less than 0.05 dB over the required range `64 MHz` for an accurate discriminator law.

Claim 11

A method for optimizing the parameters of a multiplexing filter having a plurality of individual channel bandpass filters appearing equally on two separate manifolds isolated by a power divider, with the properties of channelized filtering and channelized linear frequency discrimination, comprising the steps of: a. providing a lumped equivalent circuit representation of two adjacent channel filters, one on each manifold, selected from said plurality for analysis with respect to linearity of frequency discrimination; b. providing a set of initial parameter values for the circuit element of said equivalent circuit representation and sample frequencies at which peak error values are likely to occur for the frequency range between the center frequencies of said two adjacent bandpass filters; c. calculating, for all pairs of adjacent channel filters, the differential amplitude between the signal output of the first of any of said two adjacent filters and that of the second at the frequencies of the predicted error extreme; d. computing an error result representing the difference between said differential amplitude and a straight-line law vs. frequency; e. computing the derivatives of said errors with respect to all optimizable parameters and with respect to frequency; f. changing said initial parameter values to values predicted by said computed derivative values; g. repeating steps c, d, e and f until errors at said sample peaks are reduced and said sample peaks coincide with actual peaks in said error, such that the error in the frequency discriminator curve relative to a straight line law is a minimum equal-ripple value over the desired frequency range; h. applying the results of said previous steps to all adjacent filter channels in said multiplexing filter, thereby optimizing the values of the circuit parameters for each of said bandpass filters to yield a bandpass response shape such that the ratios of the output levels of all pairs of adjacent channel filters is linear with respect to a straight-line law for dB vs. frequency range between the center frequencies of said pairs of adjacent channel, each channel working with its higher and lower-frequency neighbors to produce this same result; and i. tuning each filter to match the universal response with linear frequency scale of appropriate bandwidth within less than 0.05 dB over the required range `64 MHz` for an accurate discriminator law.